Serial Network Flow Monitor (SNFM) - 05.13.15
The Serial Network Flow Monitor (SNFM) uses commercial off-the-shelf software to study the International Space Station’s computer network, checking the speed of data transfers and the electronic equivalent of “traffic jams.” The SNFM team monitors data transmission between the ISS and the ground, checks for delays caused by heavy use of the computer network, and troubleshoots problems.
Science Results for Everyone
“Network busy.” “Message not sent.” Anyone who uses computer networks knows they experience annoying glitches, and those on the International Space Station (ISS) are no exception. This investigation monitored the ISS payload local area network (LAN) to analyze and troubleshoot data traffic. This work could lead to more robust traffic models, resulting in faster and more reliable networks on future space missions and improved data transfer capabilities in on-orbit computer networks. Researchers are still analyzing data, which will provide useful information for ongoing network operations on spacecraft now and in the future. Experiment Details
Carl Konkel, Boeing, Houston, TX, United States
Boeing, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
April 2004 - Ongoing
Previous ISS Missions
SNFM is a continuing investigation which has been performed on ISS Expeditions 9 and 10.
- This experiment studies the function of the computer network onboard the ISS.
- On-orbit packet statistics are captured and used to validate ground based medium rate data link models and enhance the way that the local area network (LAN) is monitored.
- This information will allow monitoring and improvement in the data transfer capabilities of on-orbit computer networks.
The Serial Network Flow Monitor (SNFM) experiment attempts to characterize the network equivalent of traffic jams on board ISS. The SNFM team is able to specifically target historical problem areas including the SAMS (Space Acceleration Measurement System) communication issues, data transmissions from the ISS to the ground teams, and multiple users on the network at the same time. By looking at how various users interact with each other on the network, conflicts can be identified and work can begin on solutions.
SNFM is comprised of a commercial off the shelf software package that monitors packet traffic through the payload Ethernet LANs (local area networks) on board ISS.
SNFM watches the space station’s payload local area network (LAN) to analyze and troubleshoot data traffic. By understanding how traffic flows through the local area network, engineers could devise new faster and more efficient computer networks for future space missions.
By monitoring how the station’s computers transfer data, SNFM could improve computer access for a variety of experiments, allowing faster and better transmission from the station to the ground. Scientists can be better served with this more efficient method of data downlink.
A Commercial Off the Shelf software package is loaded from a CD-ROM to an EXPRESS rack laptop computer. SNFM ground personnel typically coordinate with other network users and/or the POIC to determine when the events they wish to monitor will occur. The SNFM investigation monitors only the medium rate data link (MRDL).
Crew loads software onto an EXPRESS Laptop Computer (ELC) for Payload LAN monitoring. Files are downlinked by ground command. Operation of SNFM by the crew will require power up of the EXPRESS Laptop and activation of the selected SNFM Autocapture template. Once activated, SNFM will monitor the network and capture packet statistics until its buffer has filled.
SNFM data are still being analyzed, and will provide "lessons learned" for ongoing network operations on space station and future spacecraft systems. (Evans et al. 2009)^ back to top
This image shows the software CD-ROM which contains the SNFM program. Image courtesy of Nasa, Johnson Space Center.
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This image shows an example of network loading displayed graphically. Image courtesy of NASA, Johnson Space Center.
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